Global Navigation Satellite Systems (GNSS) is the standard generic term for satellite navigation systems (“sat nav”) that provide autonomous geo-spatial positioning with global coverage. GNSS allows small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few metres using time signals transmitted along a line-of-sight by radio from satellites. Receivers calculate the precise time as well as position, which can be used as a reference for scientific experiments.   _{Your Comment}